Reduce to lowest terms: $- \dfrac{2}{9} \div - \dfrac{9}{2} = {?}$
Solution: Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. The reciprocal of $- \dfrac{9}{2}$ is $- \dfrac{2}{9}$ Therefore: $ - \dfrac{2}{9} \div - \dfrac{9}{2} = - \dfrac{2}{9} \times - \dfrac{2}{9} $ $ \phantom{- \dfrac{2}{9} \times - \dfrac{2}{9}} = \dfrac{-2 \times -2}{9 \times 9} $ $ \phantom{- \dfrac{2}{9} \times - \dfrac{2}{9}} = \dfrac{4}{81} $